Issue
Checking if a port is open
Product Line
Andover Continuum, EcoStruxure Building Expert, EcoStruxure Building Operation, Field Devices, Pelco, Satchwell MicroNet, Satchwell Sigma, TAC IA Series, TAC INET, TAC Vista
Environment
- TCP/IP Communication
- Command Prompt
- Telnet Command
Cause
Suspect certain network ports are blocked and need to verify
Resolution
It is possible to check if a port is open in a network by issuing the Telnet command.
Note:- Telnet operates using the TCP protocol. UDP connectivity cannot be tested using Telnet.
If a port is open, a blank screen will be seen after issuing the command:
telnet [domainname or ip] [port]
where
- [domainname or ip] is the domain name or IP address of the server being checked
- [port] is the port number the server application is listening on
For example:
telnet 192.168.0.20 9001 (to a closed port would display a connect failed message)
telnet 192.168.0.20 9003 (to an open port would display a blank screen)
To exit the Telnet session, type Ctrl + ] and then type "quit".
For how to enable Telnet in Windows 7 please see Enable Telnet Client on a Windows 7 PC
